In order to make high frequency, high power density converters practical, very high efficiency (e.g., 90%) operation is required. Synchronous rectifiers have been proposed for use in high frequency, high power density converters because of their much lower forward voltage drop than, for example, Schottky diodes. Unfortunately, however, synchronous rectifiers are typically gated using square-wave voltages generated from complex control logic which consumes more energy and occupies more space than is practical for a commercial power supply. In addition, switching losses occur unless the devices are switched with zero-voltage thereacross. Moreover, there is a lack of commercially available MOSFET's having a low on-resistance. As a result, the potential improvement in efficiency using synchronous rectification is insufficient to warrant production of a commercial power supply using this rectification technique.
Accordingly, it is desirable to eliminate losses and reduce the space required for a synchronous rectifier gate drive. Furthermore, it is desirable to provide more precise gating control in order to achieve zero-voltage switching and hence improve efficiency. To be practical, an improved synchronous rectifier gate drive must be relatively simple and easy to manufacture.